MAX11803 Maxim Integrated Products, MAX11803 Datasheet - Page 25

• Manufacturer Part Number: MAX11803
• Description: (MAX11800 - MAX11803) Ultra-Small Resistive Touch-Screen Controllers
• Manufacturer: Maxim Integrated Products

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The MAX11800–MAX11803 idle in TDM. The TIRQ output
goes low when a touch is detected on the panel indicat-
ing to the AP that a touch is present and a measurement
operation starts.
The AP requests specific panel measurements through
the serial interface. TIRQ stays low during panel setup
and measurement operations. Once a measurement is
complete (with CONT = 0), the MAX11800–MAX11803
check for the continued presence of a touch on the
panel and tag the data accordingly (see Table 6). The
duration of this operation is programmable, specified in
the touch-detect pullup timing configuration register
(0x07). After the data is tagged, the data is available for
readback
MAX11800–MAX11803 return to TDM and return control
of TIRQ to the TDM circuitry. TIRQ stays low while a
touch remains present, indicating further measurements
are required, otherwise TIRQ goes high until a new touch
is observed.
Continuous interrupt mode (CINT) allows the complete
control over the measurement operations and direct obser-
vation of the touch status of the panel. Figure 9 shows the
polling of TIRQ when other functions share the TIRQ bus. In
the illustration of Figure 9, no ‘10’ event tag is observed
because the release occurs during a TDM period.
When a touch is present on the panel in edge interrupt
mode, the MAX11800–MAX11803 return to an untimed
high-impedance mode once data tagging operations are
complete. In edge interrupt mode, the duration of a touch
is determined by the tags applied to the measurement
data. Data tagged as initial (00) or midpress (01) indicates
the user needs to continue to scan the panel until a
Figure 9. Continuous Interrupt Mode (Direct Conversion Mode)
Low-Power, Ultra-Small Resistive Touch-Screen
READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS.
SCAN INTERVAL (t
SCAN DURATION (t
through
TIRQ
PANEL
______________________________________________________________________________________
AP
SD
) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS.
) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
TDM
the
BEGINNING OF TOUCH EVENT
serial
Edge Interrupt Mode
Controllers with I
DCM SCAN
ETAG = 00
interface.
TDM
t
AP
The
DCM SCAN
release is observed. In this state, there is no need to con-
tinue monitoring the touch status prior to the next request-
ed measurement. If a panel touch is not present, data is
tagged as release (10) and the MAX11800–MAX11803
idle in TDM continuously, issuing an interrupt only when
the next panel touch is initiated.
The operation described in the preceding paragraph
makes the edge interrupt mode more efficient than the
continuous interrupt mode. However, the edge interrupt
mode requires continuous scanning of the panel until a
release (10) event is observed. Otherwise, the
MAX11800–MAX11803 do not idle in TDM and are not
able to recognize a change in touch status. New touches
are not recognized and new interrupts are not issued if a
release event is not detected before stopping the conver-
sion sequence.
ETAG = 00
Table 6. Measurement and Event Tags
(Continuous Interrupt Mode)
Touch (data valid)
N/A (not used)
No touch present (data
invalid)
Measurement in progress
(data invalid)
t
SD
MEASUREMENT
EVENT
Z1
Z2
TDM
X
Y
2
C/SPI Interface
END OF TOUCH EVENT
DCM SCAN
ETAG = 00
MTAG[3:2]
ETAG[1:0]
TDM
00
01
10
11
00
01
10
11
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